DNS Setup in OEL 5.9 for RAC 11g R2 on VirtualBox:
We are configuring below DNS server for testing purpose and basically to fulfill the requirement of demo RAC 11gR2 installation on Virtualbox with OEL5.9 OS.
Before configuring we should know little about DNS:
A DNS server is basically used to resolve the Hostname to IP address and IP address to Hostname ass well. In My case the entire hostname with domain name “rac1.db.com” is the Fully Qualified Domain name (FQDM) where “db.com” is the domain name.Subdomains are used to divide FQDM into zones.
What is Zone: Domain Name System (DNS) allows a DNS namespace to be divided up into zones, which store name information about one or more DNS domains. For each DNS domain name included in a zone, the zone becomes the authoritative source for information about that domain.A zone starts as a storage database for a single DNS domain name.
DNS Configuration:
1.Check whether DNS server rpms are installed or not (whereas It is good to include DNS server during installation of OEL 5.9:
First check dns service is running on your server or not and also Check following rpm shuold be installed:
[root@rac1 etc]# service named status
number of zones: 2
debug level: 0
xfers running: 0
xfers deferred: 0
soa queries in progress: 0
query logging is OFF
recursive clients: 0/1000
tcp clients: 0/100
server is up and running
named (pid 2857) is running…
[root@rac1 etc]# ps -ef|grep named
named 2857 1 0 18:03 ? 00:00:00 /usr/sbin/named -u named -t /var/named/chroot
root 29429 11617 0 18:48 pts/1 00:00:00 grep named
[root@rac1 etc]# rpm -qa|grep bind*
binutils-2.17.50.0.6-26.el5
bind-9.3.6-20.P1.el5_8.6
bind-utils-9.3.6-20.P1.el5_8.6
bind-chroot-9.3.6-20.P1.el5_8.6
ypbind-1.19-12.el5_6.1
bind-libs-9.3.6-20.P1.el5_8.6
[root@rac1 etc]# rpm -qa|grep cache*
libXfontcache-1.0.2-3.1
If services are not running and rpms are not installed then install the RPMs.
2.Check /etc/sysconfig/network file, your hostname should be added in this file:
My hostname= rac1.db.com
And IP=192.168.56.110
[root@rac1 etc]# more /etc/sysconfig/network
NETWORKING=yes
NETWORKING_IPV6=no
HOSTNAME=rac1.db.com
NOZEROCONF=yes
3.Main configuration file for dns is “/var/named/chroot/etc/ named.conf”.
Check there will be a sample named file but you need to change it as per your environment, you can below file as example to make your own:
[root@rac1 etc]# vi named.conf
options{
directory "/var/named/";
};
zone "db.com" {
type master;
file "db.com.zone";
allow-transfer {192.168.56.111;};
};
zone "56.168.192.in-addr.arpa" {
type master;
file "56.168.192.in-addr.arpa.zone";
};
Since we are using bind’s chroot features(chroot is a security feature in dns), so all important file will reside in /var/named/chroot directory.
4.I have created two zone file as mentioned in “/var/named/chroot/etc/ named.conf” file. One is “db.com.zone” for forward zone and “56.168.192.in-addr.arpa.zone” for reverse zone. You can use below both file content as an example:
cd /var/named/chroot/var/named
[root@rac1 named]# ls -ltr
total 32
drwxrwx— 2 named named 4096 Jul 27 2004 slaves
drwxrwx— 2 named named 4096 Aug 26 2004 data
-rw-r–r– 1 root named 781 Aug 23 19:29 56.168.192.in-addr.arpa.zone
-rw-r–r– 1 root named 593 Aug 23 19:33 db.com.zone
Vi db.com.zone
$TTL 86400
@ IN SOA db.com. root (
42 ; serial (d. adams)
3H ; refresh
15M ; retry
1W ; expiry
1D ) ; minimum
@ IN NS rac1.db.com.
@ IN NS rac2.db.com.
rac1 IN A 192.168.56.110
rac2 IN A 192.168.56.111
rac1-vip IN A 192.168.56.120
rac2-vip IN A 192.168.56.121
rac-scan IN A 192.168.56.150
rac-scan IN A 192.168.56.151
rac-scan IN A 192.168.56.152
rac1-priv IN A 192.168.49.10
rac2-priv IN A 192.168.49.11
vi 56.168.192.in-addr.arpa.zone
$TTL 86400
@ IN SOA db.com. root.rac1.db.com. (
1997022700 ; Serial
28800 ; Refresh
14400 ; Retry
3600000 ; Expire
86400 ) ; Minimum
IN NS rac1.db.com.
110 IN PTR rac1.db.com.
111 IN PTR rac2.db.com.
120 IN PTR rac1-vip.db.com.
121 IN PTR rac2-vip.db.com.
150 IN PTR rac-scan.db.com.
151 IN PTR rac-scan.db.com.
152 IN PTR rac-scan.db.com.
10 IN PTR rac1-priv.db.com.
11 IN PTR rac2-priv.db.com.
5.Change group of both zone files:
chgrp named db.com.zone
chgrp named 56.168.192.in-addr.arpa.zone
and should look like this:
[root@rac1 named]# ls -ltr
total 32
drwxrwx— 2 named named 4096 Jul 27 2004 slaves
drwxrwx— 2 named named 4096 Aug 26 2004 data
-rw-r–r– 1 root named 781 Aug 23 19:29 56.168.192.in-addr.arpa.zone
-rw-r–r– 1 root named 593 Aug 23 19:33 db.com.zone
6.Now start the name service and make in autorestart mode when server rebbots:
Chkconfig named on
Service named start
[root@rac1 named]# service named start
Starting named: [ OK ]
Service is started successfully, i.e. your dns configuration is successfully done.
And on other node of RAC, put following entry in resolv.conf
[root@rac1 named]# more /etc/resolv.conf
#; generated by /sbin/dhclient-script
domain db.com
nameserver 192.168.56.110
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